How about some daylilies? There are enough cultivars that you could always have some blooming through the season. Try Bloomingfields in CT, lots of old fashioned ones -- or Abundant Daylilies in FL (daylilies.net), many reasonably priced ones here. I prefer the old fashioned kinds myself, lots of those at Bloomingfields.

Bloomingfield's site has a chart showing the blooming times of each kind. Daylilies come in all kinds of colors including pinks to go with your roses. There are some nearly white ones that would be nice, too.

I also have some irises under or in front of (and in a couple of spots, in back of) my roses---they too come in different heights & love sun as do roses. They bloom mostly in May in NJ where I live. Schreiners (Schreinersgardens.com) has many many photos -- they specialize in them --

(Nichollsgardens.com) Nicholls Gardens carries reblooming irises & are also quite reasonably priced. You can get miniature or dwarf irises & they will make nice color in spring.

You have a different climate in TX but I'll mention the spring bulbs--daffodils & the like---and the "little guys" squill, grape hyacinth, etc --- they can be planted in front of roses, will come up every year. You would have to find ones suitable to your region.

I think your soil might be a bit too rich for roses, and even for most plants. Roses like a PH of about 6 and they need enough terra firma to hold their roots. Yours seems too organic--good for vegetables and houseplants, but not so good for roses and most perennials. A good soil is 1/3 clay, 1/3 sand, 1/3 organic. Dig your mix into your native Lubbock soil. Lavendar likes it on the dry, sandy, alkaline side. So do most woody herbs and the aliums, like garlic, which are all good companion plants for roses as they keep critters and bugs away. Mums are also good. Scabiosa is a good continuous bloomer. Also, roses prefer a deep water once a week. Their roots [should] go down like tap roots. Finally, the kinds of roses you have will (along with soil and water) determine how frequently they bloom.

I agree that Iris's go well. I have some in front of my pink climbing roses. Lavender, I have the same problem but fixed it last year. I worked a bag of builders sand into the spots where i plnated lavender and it thrived. I also have Adenaphora, which is very non fussy, light purple and about 3-4 ft high. I also add some Nicotiana, which is an annual but fills in gaps very well and goes nicely with the lavender. Let me know if you need more info on the Adenaphora.

Catsrose, 6.0 is unheard of west of the Mississippi. In the West, native soils are alkaline and may test as high as 8.8. Adding lots of organic amendments will reduce the alkalinity. What this Lubbock gardener did is the right thing to do in Texas, as her amendments will correct her high pH just enough. Many roses do well in soils 6.8-7.5 but above that can be a problem.